#define _CRT_SECURE_NO_WARNINGS 1
#include <stdio.h>
#include <stdlib.h>
#include <stdbool.h>


struct TreeNode {
    int val;
    struct TreeNode *left;
    struct TreeNode *right;
};
 


bool isUnivalTree(struct TreeNode* root)
{
    if (root == NULL)
        return true;

    if (root->left && root->left->val != root->val)
        return false;

    if (root->right && root->right->val != root->val)
        return false;

    return isUnivalTree(root->left) && isUnivalTree(root->right);
}